Marianne Gingrich, second wife of presidential candidate Newt Gingrich, gave a two-hour interview to ABC. She says that her husband of 18 years did not practice the family values he espouses on the campaign trail, and asked for an “open marriage” when confronted about his affair with his current wife, Callista.

According to Marianne, Newt Gingrich asked to be able to continue their marriage while also seeing Callista as his mistress.

“And I just stared at him and he said, 'Callista doesn't care what I do,'" Marianne Gingrich told ABC News. “He wanted an open marriage and I refused.”

Newt Gingrich's two daughters from his first marriage, Kathy Lubbers and Jackie Cushman, wrote a letter to ABC News after they heard about the interview.

They wrote, “The failure of a marriage is a terrible and emotional experience for everyone involved. Anyone who has had that experience understands it is a personal tragedy filled with regrets, and sometimes differing memories of events.

“We will not say anything negative about our father’s ex-wife. He has said before, privately and publicly, that he regrets any pain he may have caused in the past to people he loves.”

The interview will be aired on Thursday night's episode of “Nightline,” which will come after a debate on CNN and just two days before the South Carolina primary.

Newt Gingrich's affair with Callista lasted for six years prior to his divorce from Marianne in 1999.

Marianne Gingrich also said that Newt Gingrich was planning to run for president when he divorced her and Callista “was going to help him become president.”

In an earlier interview with CNN, a former friend of Newt Gingrich claimed that, when he divorced his first wife, Jackie Battley, to marry Marianne, he said, “You know and I know that (Jackie's) not young enough or pretty enough to be the wife of a president.”

It is not clear how much the interview will affect the presidential race. Newt Gingrich's divorces and affairs have already been well publicized, and he has admitted to personal failings and the need to ask for forgiveness.

Recent polls show Gingrich in a close second place with 30 percent of the vote behind Mitt Romney's 37 percent in South Carolina.